Collisional quenching of electronically excited silicon atoms, Si[3p2(1S0)], by resonance line absorption

Abstract

A kinetic study of electronically excited silicon atoms, Si[3p²(¹S₀)], 1.909 eV above the 3p²(³P₀) ground state is presented. Si(3¹S₀) was generated by the repetitive pulsed irradiation of SiCl₄ in a flow system, and the optically metastable atom was monitored photoelectrically by time-resolved resonance line absorption at λ= 390.53 nm [4s(¹P^°₁)â†� 3p²(¹S₀)]. Absolute quenching rate constants (k_Q, cm³ molecule^–1 s^–1, 300 K) are reported for the following collision partners : He (⩽ 1.3 × 10^–15), H₂(⩽ 10^–14), N₂(⩽ 10^–14), O₂(1.5 ± 0.2 × 10^–11), Cl₂(7.3 ± 0.1 × 10^–11), CO(⩽ 10^–14), NO (1.2 ± 0.05 × 10^–9), CO₂(1.7 ± 0.3 × 10^–11), N₂O(4.3 ± 0.4 × 10^–11), CH₄(9.4 ± 1.2 × 10^–11), CF₄(4.3 ± 0.8 × 10^–12), C₂H₂(1.0 ± 0.1 × 10^–10), C₂H₄(2.5 ± 0.3 × 10^–10) and SiCl₄(9.1 ± 1.4 × 10^–11). A rough correlation (in the classical sense) is observed between k_Q and the ionisation potential of the collision partners.